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1、Respiratory Failure,Dr. Sat SharmaUniv of Manitoba,Respiratory FailureDr. Sat Sha,RESPIRATORY FAILURE,“inability of the lung to meet the metabolic demands of the body. This can be from failure of tissue oxygenation and/or failure of CO2 homeostasis.”,RESPIRATORY FAILURE“inability,RESPIRATORY FAILURE
2、,Definition Respiration is gas exchange between the organism and its environment. Function of respiratory system is to transfer O2 from atmosphere to blood and remove CO2 from blood.Clinically Respiratory failure is defined as PaO2 50 mmHg.,RESPIRATORY FAILUREDefinition,Respiratory system includes:,
3、CNS (medulla) Peripheral nervous system (phrenic nerve) Respiratory muscles Chest wall Lung Upper airway Bronchial tree Alveoli Pulmonary vasculature,Respiratory system includes:C,Potential causes of Respiratory Failure,Potential causes of Respirator,HYPOXEMIC RESPIRATORY FAILURE(TYPE 1),PaO2 60mmHg
4、 with normal or low PaCO2 normal or high pHMost common form of respiratory failureLung disease is severe to interfere with pulmonary O2 exchange, but over all ventilation is maintainedPhysiologic causes: V/Q mismatch and shunt,HYPOXEMIC RESPIRATORY FAILURE(,HYPOXEMIC RESPIRATORY FAILURE CAUSES OF AR
5、TERIAL HYPOXEMIA,1.FiO22.Hypoventilation ( PaCO2) Hypercapnic 3. V/Q mismatch Respiratory failure (eg.COPD)4. Diffusion limitation ?5. Intrapulmonary shunt - pneumonia - Atelectasis - CHF (high pressure pulmonary edema) - ARDS (low pressure pulmonary edema),HYPOXEMIC RESPIRATORY FAILURE,Causes of Hy
6、poxemic Respiratory failure,Caused by a disorder of heart, lung or blood. Etiology easier to assess by CXR abnormality:- Normal Chest x-ray Cardiac shunt (right to left) Asthma, COPD Pulmonary embolism,Causes of Hypoxemic Respirator,Hyperinflated Lungs : COPD,Hyperinflated Lungs : COPD,Causes of Hyp
7、oxemic Respiratory failure (contd.),Focal infiltrates on CXR Atelectasis Pneumonia,Causes of Hypoxemic Respirator,An example of intrapulmonary shunt,An example of intrapulmonary s,Causes of Hypoxemic Respiratory Failure (contd.),Diffuse infiltrates on CXRCardiogenic Pulmonary EdemaNon cardiogenic pu
8、lmonary edema (ARDS)Interstitial pneumonitis or fibrosisInfections,Causes of Hypoxemic Respirator,Diffuse pulmonary infiltrates,Diffuse pulmonary infiltrates,Hypercapnic Respiratory Failure (Type II),PaCO2 50 mmHgHypoxemia is always presentpH depends on level of HCO3HCO3 depends on duration of hyper
9、capniaRenal response occurs over days to weeks,Hypercapnic Respiratory Failur,Acute Hypercapnic Respiratory Failure (Type II),AcuteArterial pH is lowCauses- sedative drug over dose- acute muscle weakness such as myasthenia gravis- severe lung disease: alveolar ventilation can not be maintained (i.e.
10、 Asthma or pneumonia) Acute on chronic:This occurs in patients with chronic CO2 retention who worsen and have rising CO2 and low pH.Mechanism: respiratory muscle fatigue,Acute Hypercapnic Respiratory,Causes of Hypercapnic Respiratory failure,Respiratory centre (medulla) dysfunctionDrug over dose, CV
11、A, tumor, hypothyroidism,central hypoventilationNeuromuscular disease Guillain-Barre, Myasthenia Gravis, polio, spinal injuriesChest wall/Pleural diseases kyphoscoliosis, pneumothorax, massive pleural effusionUpper airways obstruction tumor, foreign body, laryngeal edemaPeripheral airway disorder as
12、thma, COPD,Causes of Hypercapnic Respirat,Clinical and Laboratory Manifestation(non-specific and unreliable),Cyanosis - bluish color of mucous membranes/skin indicate hypoxemia- unoxygenated hemoglobin 50 mg/L - not a sensitive indicator Dyspnea - secondary to hypercapnia and hypoxemiaParadoxical br
13、eathingConfusion, somnolence and comaConvulsions,Clinical and Laboratory Manife,ASSESSMENT OF PATIENT,Careful historyPhysical ExaminationABG analysis -classify RF and help with cause 1) PaCO2 = VCO2 x 0.863 VA2) P(A-a)02 = (PiO2 - PaCO2) PaO2 RLung function OVP vs RVP vs NVPChest RadiographEKG,ASSES
14、SMENT OF PATIENTCareful h,Clinical & Laboratory ManifestationsCirculatory changes - tachycardia, hypertension, hypotensionPolycythemia - chronic hypoxemia - erythropoietin synthesisPulmonary hypertensionCor-pulmonale or right ventricular failure,Clinical & Laboratory Manifest,Management of Respirato
15、ry Failure Principles,Hypoxemia may cause death in RFPrimary objective is to reverse and prevent hypoxemiaSecondary objective is to control PaCO2 and respiratory acidosis Treatment of underlying diseasePatients CNS and CVS must be monitored and treated,Management of Respiratory Fail,Oxygen Therapy,S
16、upplemental O2 therapy essential titration based on SaO2, PaO2 levels and PaCO2Goal is to prevent tissue hypoxiaTissue hypoxia occurs (normal Hb & C.O.) - venous PaO2 60 mmHg(SaO2 90%) or venous SaO2 60%O2 dose either flow rate (L/min) or FiO2 (%),Oxygen TherapySupplemental O2,Risks of Oxygen Therap
17、y,O2 toxicity: - very high levels(1000 mmHg) CNS toxicity and seizures - lower levels (FiO2 60%) and longer exposure: -capillary damage, leak and pulmonary fibrosis - PaO2 150 can cause retrolental fibroplasia - FiO2 35 to 40% can be safely tolerated indefinitelyCO2 narcosis: - PaCO2 may increase se
18、verely to cause respiratory acidosis, somnolence and coma - PaCO2 increase secondary to combination of a) abolition of hypoxic drive to breathe b) increase in dead space,Risks of Oxygen TherapyO2 toxi,呼吸衰竭Respiratory-Failure-英文课件,呼吸衰竭Respiratory-Failure-英文课件,MECHANICAL VENTILATION,Non invasive with
19、a maskInvasive with an endobronchial tube MV can be volume or pressure cycled For hypercapnia: - MV increases alveolar ventilation and lowers PaCO2, corrects pH - rests fatigues respiratory muscles For hypoxemia: - O2 therapy alone does not correct hypoxemia caused by shunt- Most common cause of shu
20、nt is fluid filled or collapsed alveoli (Pulmonary edema),MECHANICAL VENTILATIONNon inva,呼吸衰竭Respiratory-Failure-英文课件,呼吸衰竭Respiratory-Failure-英文课件,POSITIVE END EXPIRATORY PRESSURE (PEEP),PEEP increases the end expiratory lung volume (FRC)PEEP recruits collapsed alveoli and prevents recollapseFRC inc
21、reases, therefore lung becomes more compliantReversal of atelectasis diminishes intrapulmonary shuntExcessive PEEP has adverse effects - decreased cardiac output - barotrauma (pneumothorax, pneumomediastinum) - increased physiologic dead space - increased work of breathing,POSITIVE END EXPIRATORY PR
22、ESSU,呼吸衰竭Respiratory-Failure-英文课件,PULMONARY EDEMA,Pulmonary edema is an increase in extravascular lung waterInterstitial edema does not impair functionAlveolar edema cause several gas exchange abnormalitiesMovement of fluid is governed by Starlings equation QF = KF (PIV - PIS ) + ( IS - IV ) QF = ra
23、te of fluid movement KF = membrane permeability PIV & PIS are intra vascular and interstitial hydrostatic pressures IS and IV are interstitial and intravascular oncotic pressures reflection coefficientLung edema is cleared by lymphatics,PULMONARY EDEMAPulmonary edema,Adult Respiratory distress Syndr
24、ome (ARDS),Variety of unrelated massive insults injure gas exchanging surface of LungsFirst described as clinical syndrome in 1967 by Ashbaugh & Petty Clinical terms synonymous with ARDS Acute respiratory failure Capillary leak syndrome Da Nang Lung Shock Lung Traumatic wet Lung Adult hyaline membra
25、ne disease,Adult Respiratory distress Syn,Risk Factors in ARDS,Sepsis 3.8% Cardiopulmonary bypass 1.7% Transfusion 5.0% Severe pneumonia 12.0% Burn 2.3% Aspiration 35.6% Fracture 5.3% Intravascular coagulopathy 12.5% Two or more of the above 24.6%,Risk Factors in ARDSSepsis,PATHOPHYSIOLOGY AND PATHO
26、GENESIS,Diffuse damage to gas-exchanging surface either alveolar or capillary side of membrane Increased vascular permeability causes pulmonary edemaPathology: fluid and RBC in interstitial space, hyaline membranesLoss of surfactant: alveolar collapse,PATHOPHYSIOLOGY AND PATHOGENES,CRITERIA FOR DIAG
27、NOSIS OF ARDS,Clinical history of catastrophic event Pulmonary or Non pulmonary (shock, multi system trauma) Exclude chronic pulmonary diseases left ventricular failure Must have respiratory distress tachypnea 20 breath/minute Labored breathing central cyanosis CXR- diffuse infiltrates PaO2 O.6 Comp
28、liance 50 ml/cm H2O increased shunt and dead space,CRITERIA FOR DIAGNOSIS OF ARDS,ARDS,ARDS,MANAGEMENT OF ARDS,Mechanical ventilation corrects hypoxemia/respiratory acidosisFluid management correction of anemia and hypovolemiaPharmacological intervention Dopamine to augment C.O. Diuretics Antibiotics Corticosteroids - no demonstrated benefit early disease, helpful 1 week laterMortality continues to be 50 to 60%,MANAGEMENT OF ARDSMechanical v,呼吸衰竭Respiratory-Failure-英文课件,呼吸衰竭Respiratory-Failure-英文课件,
